Under the circumstance where the circuit density of multilevel integrated circuit devices is continuously increasing, the performance of electrical device depends on the speed of electric wire and for reducing resistance and capacity in the electric wire, accumulative capacity of interlayer insulating films needs to be lowered.
In this regard, U.S. Pat. Nos. 3,615,272; 4,399,266; and 4,999,397 disclose the formation of insulating films by SOD(spin on deposition) method using polysilsesquioxanes having dielectric constant of 2.5-3.1 as well as good planarization properties, instead of using Conventional SiO2 layer that has dielectric constant of 4.0 and is formed by CVD(chemical vapor deposition) method using.
Polysilsesquioxanes as well as preparation methods thereof are well known in the art. For example, U.S. Pat. No. 3,615,272 discloses a method of preparing a completely condensed, soluble hydrogensilsesquioxane resin, which comprises the steps of condensing trichlorosilanes in a sulfuric acid medium and washing the resulting resin with water or aqueous sulfuric acid. Also, U.S. Pat. No. 5,010,159 discloses a method of synthesizing a soluble condensed hydridosilicon resin, which comprises the steps of hydrolyzing hydridosilanes in an arylsulfuric acid hydrate-containing hydrolysis medium and contacting the resulting resin with a neutralizing agent. U.S. Pat. No. 6,232,424 describes a highly soluble silicon resin composition having excellent solution stability, which was prepared by hydrolyzing and polycondensing tetraalkoxysilane, organosilane and organotrialkoxysilane monomers in the presence of water and a catalyst. U.S. Pat. No. 6,000,339 describes that a silica-based compound is useful for improving the resistance to oxygen plasma and physical properties as well as thickness of a coating film, which can be obtained through reacting a monomer selected from the group consisting of alkoxysilane, fluorine-containing alkoxysilane and alkylalkoxysilane with a titanium- or zirconium-alkoxide compound in the presence of water and a catalyst. U.S. Pat. No. 5,853,808 describes that silsesquioxane polymers useful for forming SiO2-rich ceramic coating can be obtained from hydrolysis and polycondensation of organosilanes having a β-substituted alkyl group.
However, any of these prior polysilsesquioxane resins do not have a dielectric constant that is low enough to meet the current requirements for an interlayer insulating film in the field of highly integrated semiconductor devices. Additionally, there has been demand for an interlayer insulating film that was improved in other physical properties including mechanical properties, thermal stability, crack-resistance, and so on.